How many moles of solute are in 250 mL of 2.0M #CaCl_2#? How many grams of #CaCl_2# is this?

1 Answer
Ernest Z.
Aug 4, 2016

The solution contains 0.50 mol or 55 g of #"CaCl"_2#.

Moles of #"CaCl"_2#

You know there are 2.0 mol of #"CaCl"_2# in 1 L of solution.

In 250 mL of solution there are

#"0.250" cancel("L soln") × "2.0 mol CaCl"_2/(1 cancel("L soln")) = "0.50 mol CaCl"_2#

Mass of #"CaCl"_2#

The mass of 1 mol of #"CaCl"_2# is

#"(40.08 + 2 × 35.45) g" = "(40.08 + 70.90) g" = "110.98 g"#.

So the mass of #"0.50 mol of CaCl"_2# is

#"0.50" cancel("mol CaCl"_2) × "110.98 g CaCl"_2/(1 cancel("mol CaCl"_2)) = "55 g CaCl"_2#

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